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Re: [m2m-iwg] COAP
David, thanks very much for your contribution, it's helpful to have someone "in the know"! Also useful to understand some of the differences here.

We discussed CoAP briefly on the Paho project call today. One of the questions that came up was around implementations and licensing (I think particularly in relation to involvement at OneM2M). Essentially we're currently not CoAP experts but, should an implementation come to us and be donated to the project, we would be interested in looking at it. Are there any *EPL-compatible* CoAP implementations that it would make sense for us to consume? - assuming that the role of Paho is to be a home of solid implementations of Open Standards messaging protocols for IoT/M2M.

Andy


On Tue, Apr 16, 2013 at 5:28 PM, Navarro, David <david.navarro@xxxxxxxxx> wrote:

Hi all,

 

Please allow me to jump in. I’m working for Intel’s Opensource Technology Center and I participated in the development of OMA’s LWM2M (which relies on CoAP as Julien said).

 

I don’t think CoAP and MQTT are designed to answer the same use cases. MQTT (as I understand it) is all about publishing events with a subscribe mechanism. CoAP is designed to be a replacement of HTTP in constrained environments. So even if CoAP features an Observe mechanism to be notified of value changes, it is not its main purpose and in this, it will be inferior to MQTT. And as an HTTP equivalent, CoAP makes no assumption on the system topology.

At the OMA, we choose to base LWM2M protocol on CoAP because it provides the core functionnalities of HTTP (GET, PUT, POST, DELETE commands, TLS security) in a reduced footprint. The Observe mechanism is a nice-to-have feature but not essential in the LWM2M use-case.

 

Regards,

David Navarro

 

From: m2m-iwg-bounces@xxxxxxxxxxx [mailto:m2m-iwg-bounces@xxxxxxxxxxx] On Behalf Of Matteo Collina
Sent: Monday, April 15, 2013 6:19 PM


To: m2m Industry Working Group
Subject: Re: [m2m-iwg] COAP

 

The real difference between CoAP and MQTT is in how the notification of events works:

In practice, it is the "gateway" or end-user that start observing for changes on the sensor.

In MQTT, it is the other way around, it is the sensor that publishes stuff on a broker.

However CoAP allows some true P2P communication between devices, which is not possible in a central system like MQTT. 

 

It has a real difference, and it may be the reason because it lacks adoption.

I think deploying a central client-server system is much easier.

 

Cheers,

 

Matteo

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